Refining processes for a renewable oil

ABSTRACT

The invention relates generally to methods of refining a renewable oil, such as a biofuel. In some embodiments, the invention relates to methods for the efficient removal of gums and waxes from a renewable oil.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is nonprovisional of, and claims the benefit of U.S.Patent Application No. 61/830,923 filed Jun. 4, 2013, the entirecontents of which is incorporated herein by reference for all purposes.

FIELD OF THE INVENTION

The invention relates generally to methods of refining a renewable oil,such as a biofuel. In some embodiments, the invention relates to methodsfor the efficient removal of gums and waxes from a renewable oil.

BACKGROUND

Crude vegetable oils and other biofuels can contain waxes and gums thatprecipitate as solids under certain operating conditions, giving acloudy appearance to the oil. While these waxes and gums can result froma variety of impurities in the oil, they are often the result ofphosphorus-containing impurities in the oil. Such phosphorus-containingimpurities can include phosphatides, such as hydratable phosphatides andnon-hydratable phosphatides. These impurities can enter the oil from avariety of sources. These impurities can be present in the oil for avariety of reasons. In some instances, the impurities are presentbecause of certain processing steps used in the initial processing ofthe oil. For example, such impurities can result from certain processingstops to remove free fatty acids from biodiesel or to remove free fattyacids from corn oil obtained from ethanol plants. The presence of theseimpurities in the oil can render the oil unusable as a fuel source, or,if usable, can limit its operating range. Therefore, it is desirable toremove such impurities from the renewable oil.

One can employ various means to remove these waxes and gums from theoil. Such techniques include water degumming, acid degumming, acidrefining, dry degumming, enzymatic degumming, degumming by chelatingagents, ultra-filtration and cavitation. Many of these process requirewashing of the oil, either as part of the process itself or to removechemicals that are added to facilitate the process. Such washing cancause substantial loss of oil, thereby lowering the efficiency of theprocess and increasing the operating costs. In some cases, such as withenzymatic degumming, the materials are expensive, and add considerablecosts to the process. Other processes require expensive equipment, whichincrease the capital expenditures involved in carrying out the process.Therefore, there is a need to continue to develop refining processesthat can be carried out quickly with minimal oil loss, do not involveexpensive reagents, and do not require expensive equipment.

SUMMARY OF THE INVENTION

In at least one aspect, the invention provides methods of reducing thecloud point of a renewable oil, the method comprising: providing arenewable of which comprises waxy impurities; cooling the renewable oil;adding a polymer to the cooled renewable oil; mixing the cooledrenewable oil and the polymer to form an oil-polymer mixture, whichcomprises solidified impurities; and separating at least a portion ofthe solidified impurities from the oil-polymer mixture to form a refinedrenewable oil.

In another aspect, the invention provides methods of reducing the cloudpoint of a renewable oil, the method comprising: providing a renewableoil, wherein the renewable of comprises phosphorus-containing compounds,free fatty acids, or a combination thereof; cooling the renewable oil;adding a polymer to the cooled renewable oil; binding the polymer to thephosphorus-containing compounds, the free fatty acids, or both thephosphorus-containing compounds and the free fatty acids; and separatingat least a portion of the polymer to form a refined renewable oil.

Other aspects and embodiments of the invention are described in furtherdetail in the following sections.

BRIEF DESCRIPTION OF THE DRAWINGS

The application includes the following figures. These figures depictscertain illustrative embodiments of various aspects of the invention. Insome instances, the figures do not necessarily provide a proportionalillustration of an actual embodiment of the invention, but may emphasizecertain features for purposes of illustration. The figures are notintended to limit the scope of the claimed subject matter apart from anexpress indication to the contrary.

FIG. 1 depicts a flow diagram for a process for removing a waxy impurityfrom a renewable oil.

FIG. 2 depicts a flow diagram for a process hr removing a waxy impurityfrom a renewable oil

FIG. 3 depicts a flow diagram for a process of refining biodiesel.

DETAILED DESCRIPTION

The following description recites various aspects and embodiments of thepresent invention. No particular embodiment is intended to define thescope of the invention. Rather, the embodiments merely providenon-limiting examples various compositions, apparatuses, and methodsthat are at least included within the scope of the invention. Thedescription is to be read from the perspective of one of ordinary skillin the art; therefore, information well known to the skilled artisan isnot necessarily included.

Definitions

As used herein, the articles “a,” “an,” and “the” include pluralreferents, unless expressly and unequivocally disclaimed.

As used herein, the conjunction “or” does not imply a disjunctive set.Thus, the phrase “A or B is present” includes each of the followingscenarios: (a) A is present and B is not present; (b) A is not presentand B is present; and (c) A and B are both present. Thus, the term “or”does not imply an either/or situation, unless expressly indicated.

As used herein, the term “comprise,” “comprises,” or “comprising”implies an open set, such that other elements can be present in additionto those expressly recited.

Unless otherwise indicated all numbers expressing quantities ofingredients, reaction conditions, and so for used in the specificationare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters sot forth in the following specification are approximationsthat can vary depending upon the desired properties sought to beobtained by the present invention. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all subranges subsumedtherein. For example, a stated range of “1 to 10” should be consideredto include any and all subranges between (and inclusive of) the minimumvalue of 1 and the maximum value of 10; that is, all subranges beginningwith a minimum value of 1 or more, e.g. 1 to 6.1 and ending with amaximum value of 10 or less, e.g., 5.5 to 10.

Other definitions are provided throughout the specification. When anyterm is not specifically defined, the term shall have the meaning thatit would have to persons of ordinary skill in the field to which theinventions disclosed herein are directed.

Refining Processes

In at least one aspect, the invention provides methods of reducing thecloud point of a renewable oil, the method comprising: providing arenewable oil, which comprises waxy impurities; cooling the renewableoil; adding a polymer to the cooled renewable oil; mixing the cooledrenewable oil and the polymer to form an oil-polymer mixture, whichcomprises solidified impurities; and separating at least a portion ofthe solidified impurities from the oil-polymer mixture to form a refinedrenewable oil.

In another aspect, the invention provides methods of reducing the cloudpoint of a renewable oil, the method comprising: providing a renewableoil, wherein the renewable oil comprises phosphorus-containingcompounds, free fatty acids, or a combination thereof; cooling therenewable oil; adding a polymer to the cooled renewable oil; binding thepolymer to the phosphorus-containing compounds, the free fatty acids, orboth the phosphorus-containing compounds and the free fatly acids; andseparating at least a portion of the polymer to form a refined renewableoil.

As used herein, the term “renewable oil” refers to any organic liquidhaving renewable source. Renewable oils can include fatty acid esters,such as those commonly used in biodiesel. Thus, in some embodiments, therenewable oil comprises fatty acid esters, such as methyl, ethyl,isopropyl, and propyl esters of certain fatty acids, such as saturatedfatty acids, monounsaturated fatty acids, polyunsaturated fatty acids,and trans-fatty acids. Renewable oils can also include varioustriglycerides, such as those obtained from various animal or vegetablesources. The invention is not limited to any particular renewable sourcefor the renewable oil, and can at least include one or more of thefollowing: animal fats, including but not limited to tallow, lard,grease, chicken fat, and by-products of fish or shellfish processing;vegetable oils, including but not limited to rapeseed oil, soybean oil,corn oil, palm oil, jatropha oil, mustard oil, jojoba oil, flax oil,coconut oil, peanut oil, hemp oil, castor oil, and sunflower oil; wastevegetable oil; by-products of ethanol production; and sewage sludge. Insome embodiments, the renewable oil comprises a vegetable oil, an animaloil, or a mixture thereof. In some embodiments, the renewable oilcomprises a vegetable oil, such as corn oil. In some embodiments, therenewable oil comprises a crude renewable oil, such as renewable of thathas not yet undergone any refining process. In some other embodiments,the renewable oil comprises a partially refined renewable oil, which hasundergone one or more processing steps. In some embodiments, therenewable oil comprises crude corn oil. In some other embodiments, therenewable oil comprises partially refined corn oil. In some embodiments,the renewable oil comprises crude biodiesel. In some other embodiments,the renewable oil comprises a partially refined biodiesel.

As used herein, “cloud point” refers to the temperature at which solidcrystals first appear in the oil when the oil is tested according to theprocedure set forth in the ASTM D2500 specification, which is publishedby the American Society for Testing and Materials, West Conshohocken,Pa., USA. This method of measuring the cloud point if often referred toin the art as the “manual method.”

The methods include providing a renewable oil. As used herein, the term“providing” is broadly defined, and can include the delivery of therenewable oil for the carrying out of the additional steps in theprocess.

The renewable oil can include certain impurities. In some embodiments,these impurities include waxy impurities. As used herein, the term “waxyimpurities” refers to various waxes and gums that can be present in therenewable oil. In some instances, these substances can dissolve in therenewable oil, but tend to precipitate as the temperature of therenewable oil is lowered. The presence or quantity of such waxyimpurities can be measured indirectly by the determining the cloud pointof the renewable oil, as described above. In some embodiments, the waxyimpurities include one or more phosphorus-containing compounds. Suchcompounds can come from a variety of sources. In some embodiments, thephosphorus-containing compounds can include certain phospholipids, orthe byproducts thereof, which can occur naturally in most vegetableoils, and can be present to a lesser degree in certain animal fats. Insome embodiments, the phosphorus-containing compounds can includeresidues or remnants of certain materials employed in an earlierprocessing step in the refining process. In some such embodiments, thephosphorus-containing compounds can result from the use of certainphosphorus-based soaps in the refining process. In some embodiments, thephosphorus-containing compounds include phosphatides, includinghydratable phosphatides, non-hydratable phosphatides, or mixturesthereof.

In some embodiments, the renewable oil comprises one or more free fattyacids as an impurity. As used herein, the term “free fatty acids” refersto fatty acids in the free acid form, e.g., not as part of an ester.Such impurities can occur in biodiesel and in vegetable and animal oils.They can occur for a variety of reasons. For example, in sonicinstances, free fatty acids can be generated as a by-product of certaintrans-esterification processes. In other instances, the free fatty acidscan be present in the oil as the result of degradation, e.g., naturaldegradation or degradation due to previous use or processing of the oil.

The methods include adjusting the temperature of the renewable oil. Insome embodiments, the adjusting comprises cooling the renewable oil. Theinvention is not limited to any particular means of cooling the oil. Anysuitable means of cooling the oil can be used, as are well known in theindustry. The renewable oil is generally cooled to a temperature belowstandard room temperature, e.g., below 25° C. In some embodiments, thecooling comprises cooling the renewable oil to a temperature within 10°C., or within 7° C., or within 5° C., or within 3° C. of the cloud pointof the renewable oil. In some such embodiments, the cooling comprisescooling the renewable oil to a temperature below the cloud point of theoil. In some other such embodiments, the cooling comprises cooling therenewable oil to a temperature above the cloud point of the oil. In someembodiments, the cooling comprises cooling the renewable oil to atemperature below 20° C., or below 15° C., or below 10° C., or below 7°C., or below 5° C., or below 3° C. or below 1° C. or below 0° C., orbelow −1° C., or below −3° C., or below −5° C. The degree of cooling candepend on various factors, including the composition of the renewableoil, the chemical makeup of any impurities, and the quantity of anyimpurities.

The methods include adding a polymer to the cooled renewable oil. Thepolymer can be added or introduced to the renewable oil by any suitablemeans. The invention is not limited to any particular polymer. In someembodiments, the polymer is an insoluble polymer, meaning that at least70%, or at least 80%, or at least 90%, or at least 95%, or at least 97%,or at least 99% of the polymer is insoluble in the renewable oil at thequantities added. In some embodiments, the polymer is an edible organicpolymer. In some embodiments, the polymer is polyvinyl polypyrrolidone(PVPP). The invention is not limited to the use of any particularquantity of polymer. The amount of polymer will vary depending on thenature of the renewable oil and the concentration of various impuritiesin the oil. In some embodiments, the polymer is added to the renewableoil at a concentration of 0.5 to 10 weight percent, based on the totalweight of the oil-polymer mixture.

The method includes various ways of contacting the polymer with theimpurities that are sought to be removed from the renewable oil. In someembodiments, the method includes mixing the cooled renewable oil and thepolymer to form an oil-polymer mixture, which comprises solidifiedimpurities. The invention is not limited to any particular method ofmixing or the use of any particular mixer. For example, any suitableindustrial mixer can be used. The oil-polymer mixture includes varioussolidified impurities, i.e., precipitated impurities, that mayprecipitate out of the oil, for example, by the cooling of the oil or bythe presence of the polymer, or both. In some embodiments, a substantialnumber of the solidified impurities, for example, at least 60%, or atleast 70%, or at least 80%, or at least 90%, bind to the added polymer.

In such embodiments, the method generally includes separating at least aportion of the solidified impurities from the oil-polymer mixture toform a refined renewable oil. Any suitable amount of the impurities canbe removed. In some embodiments, at least 60%, or at least 70%, or atleast 80%, or at least 90%, of the solidified impurities are separatedfrom the renewable oil. The separating of these impurities from therenewable oil yields a refined renewable oil, which generally has alower cloud point than before the performance of the method. In someembodiments, the method reduces the cloud point of the renewable oil byat least 2° C., or by at least 4° C., or by at least 6° C. Theseparating can be performed by any suitable method, In some embodiments,the separating is performed by centrifugation.

In some other embodiments, the method includes binding the polymer tocertain impurities in the renewable oil. Such impurities can includephosphorus-containing compounds (as described above), the free fattyacids (as described above), or both the phosphorus-containing compoundsand the free fatty acids.

In such embodiments, the method generally includes separating at least aportion of the polymer to form a refined renewable oil. Any suitableamount of the polymer can be removed. In some embodiments, at least 70%,or at least 80%, or at least 90%, or at least 95%, or at least 97%, orat least 99% of the polymer is separated from the renewable oil. Theseparating of the polymer from the renewable oil yields a refinedrenewable oil, as the polymer binds to certain impurities in therenewable oil. Once the method if performed, the resulting refinedrenewable oil generally has a lower cloud point than before theperformance of the method. In some embodiments, the method reduces thecloud point of the renewable oil by at least 2° C. or by at least 4° C.,or by at least 6° C. The separating can be performed by any suitablemethod. In some embodiments, the separating is performed bycentrifugation. In some other embodiments, the separating is performedby filtering. In some further embodiments, the separating is performedby settling.

The practice of the above methods can impart other benefits in additionto those described. For example, the methods also have the effect ofremoving unwanted soaps from the renewable oil. Further, the methods canremove certain colors (or discoloration) from the renewable oil. In someembodiments, bleaching clay is added to the renewable oil to removecertain colors from the oil. The bleaching clay is then subsequentlyseparated from the renewable oil according to any of the separatingtechniques described above or known in the art.

In another aspect, the invention provides methods of reducing the cloudpoint of a renewable oil, the method consisting essentially of:providing a renewable oil, which comprises waxy impurities; cooling therenewable oil; adding a polymer to the cooled renewable oil; mixing thecooled renewable oil and the polymer to form an oil-polymer mixture,which comprises solidified impurities; and separating at least a portionof the solidified impurities from the oil-polymer mixture to form arefined renewable oil. The various embodiments of these features aredescribed above, and are incorporated herein by reference.

In another aspect, the invention provides methods of reducing the cloudpoint of a renewable oil, the method consisting essentially of:providing a renewable oil, wherein the renewable oil comprisesphosphorus-containing compounds, free fatty acids, or a combinationthereof; cooling the renewable oil; adding a polymer to the cooledrenewable oil; binding the polymer to the phosphorus-containingcompounds, the free fatty acids, or both the phosphorus-containingcompounds and the free fatty acids; and separating at least a portion ofthe polymer to form a refined renewable oil. The various embodiments ofthese features are described above, and are incorporated herein byreference.

FIG. 1 depicts a flow chart of one method of reducing the cloud point ofa renewable oil 100, the method includes: providing a renewable oil,which comprises waxy impurities 101; cooling the renewable oil 102;adding a polymer to the cooled renewable oil 103; mixing the cooledrenewable oil and the polymer to form an oil-polymer mixture, whichcomprises solidified impurities 104; and separating at least a portionof the solidified impurities from the oil-polymer mixture to form arefined renewable oil 105.

FIG. 2 depicts a flow chart of one method of reducing the cloud point ofa renewable oil 200, the method includes: providing a renewable oil,wherein the renewable oil comprises phosphorus-containing compounds,free fatty acids, or a combination thereof 201; cooling the renewableoil 202; adding a polymer to the cooled renewable oil 203; binding thepolymer to the phosphorus-containing compounds, the free fatty acids, orboth the phosphorus-containing compounds and the free fatty acids 204;and separating at least a portion of the polymer to form a refinedrenewable oil 205.

In some embodiments, the above methods can be incorporated into a largerrefining process, such as the refining of biodiesel. FIG. 3 shows a flowchart for a biodiesel refinery process 300, which includes: drying andfiltering the raw oil 301; adding acid to effect high free fatty acidesterification 302; performing trans-esterification to yield biodiesel303; removing methanol or other alcohols from the trans-esterification304; washing the product with water or another aqueous medium 305; drythe product 306; performing wax removal according to any of theabove-described embodiments 307; removal of color 308 to achieve afinished biodiesel 309.

EXAMPLE

A crude corn oil sample (100 kg) is obtained, which contains about 14weight percent free fatty acids and also contains certainphosphorus-containing compounds, such as phospholipids or theirderivatives. The oil is cooled in a refrigerated tank to about −6° C. Anamount of PVPP (1-2 kg) is added, and mixed into the renewable oil usingan industrial mixer. The polymer is mixed into the oil for about 5minutes, while maintaining the oil at a temperature of about −6° C. Theresulting oil-polymer mixture is centrifuged, so as to separateprecipitated particles from the renewable oil. The refined oil is thencollected. About 95% of the original oil is recovered in the process.The cloud point is reduced by 4° C.

1. A method of reducing the cloud point of a renewable oil, the methodcomprising: providing a renewable oil, which comprises waxy impurities;cooling the renewable oil; adding a polymer to the cooled renewable oil:mixing the cooled renewable oil and the polymer to form an oil-polymermixture, which comprises solidified impurities; and separating at leasta portion of the solidified impurities from the oil-polymer mixture toform a refined renewable oil.
 2. The method of claim 1, wherein therenewable oil comprises a vegetable oil, an animal oil, or a mixturethereof.
 3. The method of claim 1, wherein the renewable oil comprisescorn oil.
 4. The method of claim 1, wherein the renewable oil is a cruderenewable oil.
 5. The method of claim 1, wherein the renewable oil is arenewable oil that is at least partially refined.
 6. The method of claim1, wherein the waxy impurities comprise one or morephosphorus-containing compounds.
 7. The method of claim 6, wherein theone or more phosphorus-containing compounds comprise hydratablephosphatides, non-hydratable phosphatides, or a mixture thereof.
 8. Themethod of claim 1, wherein the cooling comprises cooling the renewableoil to a temperature below 5° C.
 9. The method of claim 1, wherein thecooling comprises cooling the renewable oil to a temperature below 3° C.10. The method of claim 1, wherein the cooling comprises cooling therenewable oil to a temperature below 1° C.
 11. The method of claim 1,wherein the polymer is an edible organic polymer.
 12. The method ofclaim 1, wherein the polymer is a polyvinyl polypyrrolidone polymer. 13.The method of claim 1, wherein the separating comprises centrifuging theoil-polymer Mixture.
 14. The method of claim 1, wherein the cloud pointof the refined renewable oil is at least 2° C. lower than the cloudpoint of the renewable oil.
 15. The method of claim 1, wherein the cloudpoint of the refined renewable oil is at least 4° C. lower than thecloud point of the renewable oil.
 16. The method of claim 1, wherein thecloud point of the refined renewable oil is at least 6° C. lower thanthe cloud point of the renewable oil.
 17. A method of reducing the cloudpoint of a renewable oil, the method comprising: providing a renewableoil, wherein the renewable oil comprises phosphorus-containingcompounds, free fatty acids, or a combination thereof; cooling therenewable oil; adding a polymer to the cooled renewable oil; binding thepolymer to the phosphorus-containing compounds, the free fatty acids, orboth the phosphorus-containing compounds and the free fatty acids; andseparating at least a portion of the polymer to form a refined renewableoil.
 18. The method of claim 18, wherein the renewable oil comprises avegetable oil, an animal oil, or a mixture thereof.
 19. The method ofclaim 18, wherein the renewable oil comprises corn oil.
 20. The methodof claim 18, wherein the renewable oil is a crude renewable oil.
 21. Themethod of claim 18, wherein the renewable of is a renewable oil that isat least partially refined.
 22. The method of claim 18, wherein therenewable oil comprises phosphorus-containing compounds, and the bindingstep comprises binding the polymer to the phosphorus-containingcompounds.
 23. The method of claim 23, wherein the one or morephosphorus-containing compounds comprise hydratable phosphatides,non-hydratable phosphatides, or a mixture thereof.
 24. The method ofclaim 18, wherein the renewable of comprises free fatty acids, and thebinding step comprises binding the polymer to the free fatty acids. 25.The method of claim 18 where the binding step comprises mixing thecooled renewable oil and the polymer to form an oil-polymer mixture. 26.The method of claim 18, wherein the cooling comprises cooling therenewable oil to a temperature below 40° C.
 27. The method of claim 18,wherein the cooling comprises cooling the renewable oil to a temperaturebelow 36° C.
 28. The method of claim 18, wherein the cooling comprisescooling the renewable oil to a temperature below 33° C.
 29. The methodof claim 18, wherein the polymer is an edible organic polymer.
 30. Themethod of claim 18, wherein the polymer is a polyvinyl polypyrrolidonepolymer.
 31. The method of claim 18, wherein the separating comprisescentrifuging.
 32. The method of claim 18, wherein the cloud point of therefined renewable oil is at least 2° C. lower than the cloud point ofthe renewable oil.
 33. The method of claim 18, wherein the cloud pointof the refined renewable oil is at least 4° C. lower than the cloudpoint of the renewable oil.
 34. The method of claim 18, wherein thecloud point of the refined renewable oil is at least 6° C. lower thanthe cloud point of the renewable oil.